Combined valve and relay structure in burner control system



Aug. 13, 1963 J. A. DEUBEL 3,100,521

COMBINED VALVE AND RELAY STRUCTURE IN BURNER CONTROL SYSTEM Filed Feb. 3, 1958 I 5 Sheets-Sheet 1 dl/677A/ A2 051/562 INVENTOR.

BY r w #TTUQNEWS Aug. 13, 1963 J. A. DEUBEL 3,100,521

COMBINED VALVE AND RELAY STRUCTURE IN BURNER CONTROL SYSTEM Filed Feb. 3, 1958 3 Sheets-Sheet 2 es 696 l 4 EG- JUST/N 6 05U6EZ,

INVENTOR.

BY 7 W170 Aug. 13, 1963 J- A. DEUBEL COMBINED VALVE AND RELAY STRUCTURE IN BURNER CONTROL SYSTEM Filed Feb. 5, 1958 5 Sheets-Sheet 3 77/1462 02%? i Mame .T. @414 L/Z/STZN 0. 054/554 IN V EN TOR.

prroa/ s United States Patent COMBINED VALVE AND RELAY STRUCTURE lN BURNER CONTROL SYSTEM Justin A. Deubel, Milwaukee, Wis, assignor to General Controls (30., Glendale, Calii, a corporation of Qalifornia Filed Feb. 3, 1958, Ser. No. 712,853

7 Claims. (Cl. 158-125) This invention relates generally to control systems for gas burning domestic appliances and particularly to control systems for domestic gas burning clothes driers. The present application is a continuation-in-part of my now abandoned copendin-g application Serial No. 487,785, filed February 14, 1955, and [assigned to the same assignee.

With increased use of domestic clothes driers of both the gas and electric type has come increased pressure to make these appliances safer in operation and more troublefree. As the mass market for these appliances widens, there is a growing incentive to lower the cost of both the electric and gas type driers so that the competitive position of one type versus the other may be bettered. This has been particularly true in the case of gas burning driers and it has at least been suggested that this type of drier has more of a burden in this respect because the domestic users are convinced, correctly or incorrectly, that gas appliances are more dangerous than electric appliances and because more complicated and expensive control components are needed to safely control a gas appliance as compared to those necessary for control of an electric appliance.

In the past, the problem of providing for, among other things: (1) complete gas shut-off on pilot failure in the case of liquid petroleum gas, (2) automatic or manual reset of the pilot safety device after a pilot failure, (3) an interlock, either mechanical or electrical, between the safety pilot and the manual shut-ofi device to prevent short cycling, and (4) an electric igniter for the gas pilot which has a satisfactory service life, have proved troublesome. Furthermore, erratic and undep endable operation has resulted from frequent clogging of the pilot burner ports as a result of operation in the lint-contaminated atmosphere adjacent a clothes drier. Various attempts to solve the problem by purging of lint by the primary air introduced into the pilot burner have not been entirely successful.

An object of the present invention is to provide a spark ignition system for gas burning appliances, particularly clothes driers which eliminates the need for a pilot burner and pilot safety devices, but provides all the safety features heretofore associated only with systems using pilot burners and their accompanying elaborate pilot safety devices.

A further object is to provide a gas burning appliance control which incorporates an ignition system having a long, trouble-free service life.

A further object is to provide a gas burning appliance control having spark ignition operable by means. of a simplified circuit interconnecting a simplified group of control components.

Another important object of the present invention is to provide a system of this character which incorporates a combined valve and relay structure.

Another important object of the present invention is to provide a combined valve and relay structure which is particularly useful in control systems of this character.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

3,106,521 Patented Aug. 13, 1963 FIGURE 1 is a top view of components of a control system embodying features of the present invention.

FIGURE 2 is a schematic illustration of the electrical A circuit in which the components shown in FIGURE 1 are connected. 1

FIGURE 3 is an irregular sectional view of the combined electromagnetic valve and relay structure embodying features of the present invention and shown also FIG- URE 1.

FIGURE 4 is an end view of the structure shown in FIGURE 3.

FIGURE 5 illustrates a modified system.

Referring principally to FIGURES 1 and 2, there is shown at 10 a conventional gas burner of the type used on, for example, domestic gas driers, the burner 10 and other elements being mounted on a panel 13. Gas is admitted to the burner [through an inlet pipe 11, a control valve 12, and an inlet fitting 14. Valve 1'2 is a solenoid operated type valve and, in accordance with an important aspect of the present invention, is a combined valve and relay structure with the valve and relay having a com mon solenoid winding for operating simultaneously the valve portion of the structure as well as the relay switches.

Mounted adjacent burner 10 is a gas flame sensing or responsive switch assembly 16, comprising a dame detector 17 and two switch arms 16A. 168 (FIGURE 2) actuated by detector 17. The particular form of the detector 17, and the linkage through which it actuates switch arms 16A, 16B are considered to be well known in the art. In the presence of a flame the detector 17 causes the switch larms 16A, 16B to move into engagement with stationary contact and to move out of engagement with stationary contact 16D respectively to close electrical circuits which are normally open and to open norm-ally closed circuits respectively, as shown, in the absence of a flame.

Also mounted adjacent burner 10, but on the opposite side from assembly 16, is a spark ignition means 20, including mounting bracket 21, spark plug 22 with electrodes 23, 24- and lead wire 25. Lead wire 25 connects the electrode 24 to the ungrounded terminal of the secondary winding of an ignition transformer 26, the outer case of plug '22 and electrode 23 being grounded in conventional manner. Mounted just below transformer 26, as viewed in FIGURE 1, is a resistance element. 27, the function of which will be described hereafter with reference to the circuit shown in FIGURE 2.

A thermally timed safety switch is identified by reference numeral 28 and i also mounted on panel 13. Safety switch 28 is of conventional type having 'a bimetal contact actuating arm 29 (FIGURE 2),. an electric thermal operator or heater 31 (FIGURE 2') for beating the bimetal arm 29 to move such arm out of engagement with stationary contact 32. As is conventional with this type of safety switch, after arm 29 has moved sufficiently as a result of beater 31 being energized a predetermined time, the switch 29, '32 is opened and the arm 29 is latched there by latch 33 until manually reset. The latch 33 is illustrated in the form of .a cantilever supported spring having its upper bent end engageable with the free end of arm 2?, and such upper end of the spring latch may be moved manually away from the arm 29 to allow such arm 29 to move upwardly into engagement with contact 32.

Referring now to FIGURES 3 .and 4, the valve 12 includes a valve body 34 having an inlet 36 and an outlet 37. p The valve body is mounted on the panel 13. Within the valve body there is a conventional valve seat 39 and a valve .disc 40 and plunger 41 operated by the electromagnetic operator or solenoid coil 42. Coil 42 also operates an armature 4 3 which is pivoted at 44 on the generally U-shaped bracket 46. A switch actuating member 47 is carried by the armature 43 and serves to which switch 51A, 51B is closed before switch 52A, "52B is opened. The mechanical construction of the combination valve and relay is now described in connection with FIGURES 1, 3 and 4. The valve body 34 having the seat 39 has securedthereto a base plate 60 by machine screws 61 with a layer of gasket material 62, forming a seal, interposed therebetween. Such plate 60 has an inturned annular flange portion 60A within which the annular shading ring 64 of copper and plunger guide tube 65 are affixed as, for example, by press fitting, welding, brazing or the like. A sleeve 67, of shorter length than the guide tube 65, encircles the guide tube 65 near its lower end.

The coil 42 is wound on spool 68 which bears on the lower portion 46A of the generally U-shaped bracket 46, such portion 46A being retained between the coil form and the mounting plate 60. The upper end of the guide tube 65 is closed by a cylindrical plug 70 which is soldered in tube '65. A shading ring 72, of copper, is secured to the outside of such plug 70 to reduce A.C. hum wh-ich is otherwise produced when the coil is energized. The shading ring 64- accomplishes this same function for armature 97 affixed to plunger 41. It is noted that shading ring 72 encircles a part of plug 70 to provide a lagging iiux path for a portion of the ilux and prevents armature 43 from chattering.

The plunger 41 is slidably mounted in its guide tube 65, and in turn, has a valve actuating element 74 slidably mounted in it. The element 74 in the form of a rod has afiixed thereto a washer 75 which is embedded in. the closure member 40' and also carries a lock ring 77 for engagement with the plunger 41.

A coil spring 30 encircles the upper end of rod 74 and is retained loosely thereon between a lock ring 82 on rod 74, and the internal shoulder 41A of plunger 41.

The bracketmember 46 has the aforementioned base portion 46A and upstanding plate portions 46B and 46C, each of which are provided with deformable lugs 46E for securing the insulating switch carrying plate 84. This plate has riveted thereto the switch terminals 86, 87 and 88. Switch'terminal 86 carries the leaf spring 49 which carries the contacts 51B and 52B. Terminal 87 carries the leaf spring 48 which carries the contact -1A.. Terminal 88 carries the contact 52A. It is thus seen that the switch assembly (with the exception of its actuating member 47) is carried on the single plate 84.

The switch actuating member 47 of insulating material extends from a small bracket 93 mounted on the pivoted armature plate 43. This bracket 93 has a downwardly and outwardly extending portion 93A that is arranged to abut against the bracket portion 46E which acts as a stop in limiting pivotal movement of plate 43. i The plate 43 is normally biased so that these elements 93A, 46B are in engagement by the prestressed coil tension spring 96 having one of its ends hooked into an apertured portion of plate 43 and the other one of its ends hooked around one of the fastening lugs 46E. The plate 43 is conveniently retained in pivoted relationship on bracket portion 46A by spaced extensions of such bracket portion passing through spaced open-ended slatted portions of plate 43.

The following elements are of magnetizab-le material so .as to achieve the desired magnetic attract-ion; namely, plunger 41, plug 70, plate 43, U-shaped bracket 46 including 46A and mounting plate 60, and the apertured plate 97- afiixed on the lower end of plunger 41. The

4 valve actuating rod 74 is preferably of non-magnetizable material. The guide tube 65 is of non-magnetizable material such as brass.

When the coil 42 is energized the following events occur in this order. The plunger 41 which is floatingly mounted is attracted and moves upwardly a limited distance after which the upper end of the loosely mounted spring 80 engages the lock ring 82 on the actuating member 74, after which the spring 80 is compressed and causes the plunger 74 to move upwardly with the attached closure member 40 against the action of the relatively heavy coil compression spring 96 disposed between the mounting plate 60 and the spring seat 98. Spring 80 serves as a shock absorber, to absorb a hammer-like blow and thus the possibility of fracturing plunger 74. This spring 96 normally maintained the valve closed. It is noted that because of its length and rate, spring-80 exerts no force at all when plunger 41 is against ring 77, as shown. When the solenoid 42 is energized, spring 80 develops more force than spring 96; otherwise, the valve would not open. Further continued upward movement of the plunger results until the apertured plate 97 abuts the annular flange portion 60A. The field created by coil 42 causes motion of both the valve armature 41 and relay armature 43. Both of such motions is practically simultaneous and which occurs first is not considered important. When the pivoted plate 43 is attracted, it causes the switches 51A, 51B and 52A, 52B to be operated in that order.

When subsequently the coil 42 is deenergized, the spring 96 causes the valve 40 to be returned to closed position relatively rapidly and the switches 52A, 52B and 51A, 51B to be operated in that order.

The circuit which integrates all of the above described components is now described with reference to FIGURE 2. The circuit is energized by an AC. source 100 which is connected in series with tan on-oif switch 56, a thermostat 101 land the bimetallic switch comprising contact 32 and bimetallic strip 29. It is understood that the thermostat switch 191, sensitive to temperatures in the clothes drier, is closed at low temperatures and is automatically opened at higher temperatures. 7

The energizing circuit for the primary winding of ignition transformer 26 includes the following elements that are connected in series, namely, source 100, switch 56, thermostat ltil bimetallic switch 29, 32, switch 16B, '16D, resistance 27 and the primary winding of transformer 26; The switch 16B, 16D comprises an element of the flame responsive switching means 16 which is illustrated in FIGURE 2 in its cold position.

The initial energizing circuit for the solenoid coil 42 comprises the following elements which are connected in series, namely, source 100, switch 56, thermostat 101, bimetal switch 29, 32, switch 16B, 16D, switch 52A, 52B, heater 31 and coil 42. Switches 52A, 52B and 51A, 51B are illustrated in the normal positions they assume when the solenoid 42 is de-energized; and these switches, as is seen from the description of FIGURE 4, comprise essentially a single-pole double-throw switch in which, upon energization of coil 42, the switch 51A, 51B is closed before switch 52A, 52B is opened. It is noted that the switch contact 51A is connected to the movable swtich clement 16B and also to one terminal of the bimetal strip 29. Switch contacts 51B and 52B are each connected to one terminal of the heater 31 and also to the movable switch contact 16A.

The switch comprising elements 16A and 16C is connected in parallel with the heater 31 for purposes of shortcircuiting the same in the hot condition of switch 16.

It will be observed from the following detailed description that the ignition means 26 is connected in a first series circuit with heat-responsive switch 16B, 16D and that the solenoid 42 is connected in a second series circuit with its normally open relay switch 51A, 51B and that the other normally closed relay switch 52A, 52B interconnects junction points in these two series circuits; and that these two series circuits are separate branches of a parallel circuit energized from source 100. Specifically, such first series circuit, is. parallel branch, extends from bimetal element 29 through switch 16B, 161), resistance 27 to the primary winding of the ignition transformer 26; such second series circuit, i.e. second parallel bnanch, extends from the same bimetal element 29 through normally open relay switch 51A, 51B through switch element 52B, and through heater 31 to the solenoid coil 42; and the normally closed relay switch 52A, 52B interconnects junction points in these two series or branch circuits, the junction point in such first series circuit being the interconnection between stationary contact 16]) and resistance 27 and the junction point in such second series circuit being the switch element 523. Further, these two series or branch circuits are energized from source 100 having one of its terminal connected directly to a terminal of the primary winding of ignition transformer 26 and to \a terminal of the solenoid coil 42, the other terminal of source 100 being connected to the aforementioned bimetal element 29 through switch 56, thermostat 101 and bimetal contact 32.

The operation of the circuit shown in FIGURE 2 is essentially as follows. Assuming that the drier has been out of operation for a considerable length of time and is cold, the thermostat 101 is closed. At this time when the on-ofi switch 56 is closed, both the primary winding of transformer 26 and the solenoid coil 42 are energized. Such primary winding of transformer 26 and winding 42 are at this time energized through a circuit which includes source 100, switch 56, thermostat 101, switch 29, 32, switch 16B, 16D, the primary winding being energized through current limiting resistance 27, and the coil 42 being energized through switch 52A, 52B and heater 31. At this stage a gas igniting spark exists at the spark plug 22 for igniting the gas which now flows as a result of the coil 42 being energized. When coil 42 is energized, the switch 51A, 51B is closed before switch 52A, 52B is opened and such switch 51A, 51B remains closed so that the winding 42 remains continuously energized without such energizing current passing through switch 16B, 16D. In other words, energization of the coil 42 at this particular time is independent of the hot or cold condition of the heat responsive switching means 16, and gas continues to flow. Should there be no ignition of such gas for a predetermined time interval, the heater 31 becomes sufficiently heated so as to cause the bimetallic strip 29 to deflect downwardly in FIGURE 2 and to open the switch 29, 32. Should this condition occur, the bimetallic strip is latched in its circuit opening position by thelatch 33; and such switch 29, 32 may not return to its closed position until the safety switch 28 is manually reset by manual operation of the latch 33.

Assuming, however, that gas ignition has been successfully accomplished within such predetermined time interval, the flame detector 17 is heated and switching means 16 is operated and consequently switch 16A, 16C is closed and switch 16B, 16B is opened. Closing of switch 16A, 16C results in short-circuiting of the heater 31; and opening of switch 16B, 16D breaks the energizing circuit for the primary winding of ignition trans former 26.

After the drier has reached a predetermined tempenature established by the condition of thermostat 101, thej switch in such thermostat 101 opens, thereby opening since the switch 168, 16D is open and thus there cannot be a current flowing either in winding 42 or the primary winding of ignition transformer 26. This is likewise true should the on-oif switch 56 be momentarily opened and then closed.

Thus, if at the end of a cycle of the burner the flame detector 17 should fail to turn to its. cold position, switch 16B, 16D remains in open position and will prevent the start of a new on cycle. Switch 16B, 16D thus provides a check, at the end of each on cycle, as to the proper functioning of the flame responsive switching means 16. From this it will also be observed that if in the midst of a normal on cycle the control circuit should be momentarily de-energized as, for example, by momentarily opening and then closing switch 56, such reclosure of switch 56 will not cause gas to flow without ignition because winding 42 can initially only be energized through switch 163, 16D and switch 52A, 52B. The interlock provided by switch 51A, 51B assures that gas cannot be admitted to burner 10 until the flame switch 16 has assumed its cold position and switch 16B, 16D connected the igniter in the energizing: circuit.

Also, if the switch 52A should fiail to close after the end of the heating cycle, the start of a new on cycle is prevented, i.e., gas is prevented-from flowing since the energizing circuit for coil 42, which includes switch 52A, is open.

Further, if there is malfunctioning of the flame detector 17 during the initial portion of the on cycle such that, for any reason whatsoever, the switch 16A, 16C is not closed, then the heater 31 will become sufficiently heated to cause the switch 29, 32 to open and be maintained in latched position by the latch 33. In this case, manual openation of the latch 33, i.e., reset means, is required before either the solenoid 42 or spark plug 20 may again be energized.

Also, if the switch 16B, 16D should not return to its closed position after a heating cycle, gas Will be prevented from flowing, as indicated previously, due to the fact that the energizing circuit for coil 42, which includes the switch 16B, 16D, is open.

The switch elements 16A, 16B are mechanically interlocked so as to assume simultaneous operation of the same and to assure their relative positions one with respect to the other and associated stationary contacts so that, for example, should switch 16A, 160 be closed to short circuit heater 31, the switch 16B, 161D is assured of being open to prevent energization of solenoid 42.

If during a heating cycle, there be a flame failure, the switch 16 returns to its position as shown in FIG- URE 2, in which case, switch 16A, 16C is open to remove the short circuit across heater 31 to, in turn, cause the switch 29, 32 in the main energizing circuit to open and thus the fuel solenoid 42 is deenergized and the flow of fuel to the burner is stopped.

In the modified arrangement shown in FIGURE 5, the dryer motor 102 which rotates the conventional drum of a dryer is energized through switch 105 and normally closed limit switch 156 when the knob 106 of the conventional motor driven timer 107 is moved from its zero time position to a presettable time. The switch 156 is of conventional construction for the conventional purpose of de-energizing the dryer circuit when excessive temperatures are produced in the dryer and is mounted in the dryer in a conventional position where excessive temperatures might possibly result, all in accordance with prior art teachings. After the elapse of such presettable time interval, the switch 105 as well as the other timer operated switch 108 is allowed to return to their open positions. The connection between the timer 107 and its switches 105 and 103 is indicated by the dotted lines 109 and 110. The circuit shown in FIG. 5 is now described under the conditions existing when switches 105 and 108 are closed.

When switch 108 is initially closed, the primary winda 132, like the switch 29, 32 in FIGURE 2 is a safety switch which is opened only after the associated heater 131 is heated for a predetermined time interval. The

relationship between the heating element 131 and the bimetallic switch element 129 is represented by the dotted line 114. Also, at this time, the A fuel valve solenoid winding 142 is energized from source 111 through switch 156, switch 1108, switch 1116B, 116D, relay switch 152A, 152B and switch 129, 132 so as to open the fuel valve 39, 40, such winding 142 (like winding 42 in FIGURE 2) comprising the operating winding for solenoid-type fuel valve 39, 40 which controls the flow of fuel to pilot burner 139A; and this relationship is indicated by the dotted line 142A. When the winding 142 is thus energized, the normally closed relay switch 152A,

152B is opened, the normally open relay switch 151A, 151B is closed and the third relay switch; namely, relay switch 152C, which is normally open, is closed as is indicated by the dotted lines that interconnect these switches with the winding 142. Switch 151A, 151B (like switch 51A, MB in FIGURE 2) closes before switch 152A, 152B (like switch 52A, 5213 in FIGURE 2) opens so as to assure an energizing circuit for winding 142, subsequently, after the heat responsive switch 1163, M61) is opened. Closure of such third relay switch 152C conditions an'energizing circuit for the B fuel valve solenoid winding 13913 which controls the flow of fuel to the main burner 139. At this stage, the gas flowing from the pilot burner 139A, which has been ignited by the spark produced by the plug 120 burns and heats the flame rod 117' and after it has been heated to a sufficiently high degree, i.e., after some time, its associated normally closed switch 116B, 116D opens and switch 1 16A, 116C closes. Opening of switch 116B, 116D serves. to deenergize the ignition transformer 126; and, closure of switch 116A, 116C further conditions the energizing circuit for main burner solenoid winding 139B. In fact, in the cold condition of the dryer, closure of switch 116A causes the winding 139B to be energized through a circuit that includes: switch 156, switch 1108, switch '116A, 1160, switch 152C and thermostatic element 160A and thermostatic switch 160 which is operated by the thermostatic element 160A. The gas issuing from the main burner 139is ignited by the flame from the pilot burner 139A and the dryer chamber is thus heated. Should the temperature in the dryer chamber exceed a predetermined temperature established by the setting of thermostatic element 16A, switch 169 is then opened to deenergize winding 139B and thus cut off the flow of fuel to the main burner 139. Should, thereafter, the temperature inthe dryer chamber fall below said predetermined temperature, switch 160 is reclosed and fuel again is allowed to flow from the main burner 13-9 for ignition by the pilot burner 139A. After an elapse of time established by the setting of the motor driven timer 107, the switches 105 and 108 open and the system is deenergized; i.e., all flow of fuel is interrupted including that to the pilot valve operating solenoid 142.

It will be observed from the foregoing that opening of the safety switch 129, 132, for any reason, will shut down the system since, in such case the pilot solenoid 142 and the ignition transformer 126 are deenergized. This safety switch 129, 132 comprises the bimetal element 129 which is heated by the resistor 131 and which is latched in open position by the latch 133 when the 8 switch 129, 132 is opened, setting. I

Switch 129, 132 opens upon malfunctioning of the system under, for example, the following conditions: Should there be flow of unignited fuel from the pilot burner 139A or should there be insufficient flow of ignited fuel from the same burner 139A, the switch 116B, 116D will not open and the heater 131 is heated sufiiciently to open the safety switch 129, 132. In such case the heater 131 is heated by current flowing through a series circuit which includes source 111, switch 156,

thus requiring manual reswitch 108, switch 116B, 116D and heater 131. The

same result is obtained should the flame rod 117 become inoperative under normal pilot burner conditions; i.e., should the flame rod fail to open switch 116D.

It will be seen from this that proper functioning of the flame rod 117 is checked at the beginning of each drying operation and if there is failure, all gas will be cut off and manual resetting is required.

In case of power failure of short duration, occasioned by opening and closing of the line switch represented by the switch 108 or the switch 156, for example, during a heating cycle, the pilot solenoid 142 and main burner solenoid 139B rare deenergized to prevent fuel flow. Upon initial reclosure of switch 108 or switch 156, neither solenoid 142 nor solenoid 1393 will be energized since some time is required for the flame rod 117 to cool to suflioient degree to allow switch 116B, 116D to return to closed position. Switch 116B, 116D upon reclosing institutes a new cycle of events as described above in connection with closure of switch 108. During the time that switch 116B, 116D is returning towards closed position, under these conditions, the dryer motor is rotating since it is assumed that the timer switch remains closed.

It will be observed also that safety switch 129, 132 will be opened in the event of failure of the relay switch 152A, 152B to be properly operated, since if it remains in closed position with solenoid 142 energizedya heat circuit for the heater 131 is established through switches 151A, 151B and 152B, 152A; and if switch 152A, 152B fails to return to closed position, the solenoid 142 will not become energized and thus heater 131 will be heated sufficiently through switch 116B, 116D to cause safety switch 129, 132 to open.

The valves included in the system shown in FIGURE 5 and having the solenoid windings 1 42 and 1393 are considered to be constructed both mechanically and magnetically essentially as shown in FIGURE 3.

It will be observed that the arrangement shown in FIG- URE 5 may be used without the manual reset latch 133. This is so since heater 131 remains energized so long as switch 116B, 116D is closed. Such switch will serve to hold the switch 129, 132 open until electric power is removed in the event of ignition or flame failure conditions. With this arrangement, the drier, under flame failure or ignition failure conditions, completes its normal drying time cycle without the burners coming on. Power is subsequently turned off by the motorized switches 105 and 198 :and when such switches are automatically opened after the timed cycle, the warp switch 129, 132 is reset automatically during the power off time and thus is ready for a new start when power is restored upon manual operation of knob 106. It will be observed that in the arrangement shown in FIGURE 5, the heater 1 31 is connected in parallel with the warp switch 129', 132 and in the event of the heater 131 burning out, the warp switch action provided by the bimetal element 129 is not effected. In the arrangement shown in FIGURE 2, the heater is wired in series with the combination relay and valve and in the event the heater burns out, the valve will not its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. A control system for a gas-burning appliance, a main burner, a spark igniter for the main burner, a valve controlling the flow of gas to said burner, an electromagnetically operated switching mechanism and an electromagnetic operator which operates said valve and said switching mechanism, I3. flame responsive switch mechanism having a first switch closed only in the absence of flame at said burner and a second switch closed only on the presence of flame i211 said burner, a safety switch having a thermal operator adapted to move said safety switch from closed to open position a predetermined time after energization of the thermal operator, a circuit network comprising said safety switch and said first switch connected in series with each other and with two parallel circuit branches, one of said branches connecting in series the thermal operator for said safety switch and the operator for said valve, the other branch including said spark igniter, control switch means connecting said circuit network across a source of power, said second switch serving to deenergize said thermal operator when a flame appears at the burner before said predetermined time has elapsed, said network being adapted upon closure of said control switch to initially energize said valve operator, the spark igniter, and said safety switch operator and, upon the appearance of flame at said burner, to tdeenergize said igniter and to retain said valve operator energized, and circuit means including said first switch for preventing said main valve from re-opening upon momentary lde-ener-gization of said valve operator while said flame responsive switching mechanism remains in hot condition, said circuit means including a normally closed switch of said electromagnetically operated switching mechanism which controls energization of said valve operator and a normally open switch of said electromagnetically operated switch mechanism shunting said first switch and said last named normally closed switch.

2. A control system for gas burning apparatus comprising: an energizing source flame responsive means including a first normally open switch and a second normally closed switch, each of which is operated in response to heat from the flame; fuel control means including an operator therefor; a third normally open switch and a fourth normally closed switch, said third and fourth switches comprising single-pole double-throw switching means and being operated upon actuation of said fuel control means by said operator; safety switching means including a normally closed fifth switch which has associated therewith an actuator for actuating said fifth switch; igniting means; current limiting means; a first series circuit including serially said fifth switch, said second switch, said current limiting means and said igniting means; a second series circuit connectible in parallel with said current limiting means and said igniting means by said fourth switch; said second series circuit including serially said source, said fifth, second and fourth switches, said safety switch actuator and said operator; said first switch being connected in shunt with said actuator; and said third switch being effective to connect said operator directly to said safety switch through said actuator such that said second serial circuit may be energized with current flowing through said safety switch regardless of the condition of said second switch.

3. A system as set forth in claim 2 in which said singlepole double-throw switch is of the make before break type in which said third switch is closed before said fourth switch is opened.

4. In a system of the character described, a heat responsive switch; a heating element for operating said switch; flame actuated switching means including a first normally closed switch and a second normally open switch; said second switch being connected in shunt with said heating element; igniting means; fuel control means serially connected with said heating element; a single-pole double-throw switch operated when said fuel control means is energized; said single-pole double-throw switch having a movable contact connected serially with said heating element and said fuel control means; a first contact of said single-pole double-throw switch being connected both to one terminal of said first normally closed switch andalso to one terminal of said igniting means; the other terminal of said first normally closed switch being connected to one terminal of said heat responsive switch; a second contact of said single-pole double-throw switch being connected directly to said one terminal of said heat responsive switch; the other terminal of said heat reponsive switch being connectible to one terminal of a source of energizing current; the other terminal of said igniting means being connected to the other terminal of said energizing source; and said movable contact of said single-pole double-throw switch being connected to said other terminal of said energizing source through said heating element and said fuel control means.

5. A system as set forth in claim 4 in which said singlepole double-throw switch is of the make before break type.

6. In a control system of the character described for controlling the flow of gas to a burner, a gas igniting means for igniting gas at said burner, a normally closed head responsive switch which is opened by heat developed by the burner, said switch and igniting means being connected in a first series circuit, a solenoid valve including a coil for controlling the fiow of gas to said burner, said valve being opened when said coil is energized, a pair of relay switches actuated upon energization of said coil, one of said pair of relay switches being normally open and actuated to closed position when said coil is energized, a second series circuit which includes said one relay switch and said coil connected in series, said heat responsive switch being connected to said igniting means at a first junction point, said one relay switch being connected to said coil at a second junction point, the other of said pair of relay switches being normally closed and serving to normally interconnect said first junction point to means connecting said second junction point, said first and second series circuits in parallel with each other to form two parallel branches, and an energizing source connected to each of said branches to produce a current flow through said igniting means in the normal position of said heat responsive switch and to produce a current flow through said coil alternately through said one and the other relay switch.

7. A system as set forth in claim 6 in which said pair of relay switches are of the make before break type in which said one switch is closed before said other relay switch is opened.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A CONTROL SYSTEM FOR A GAS-BURNING APPLIANCE, A MAIN BURNER, A SPARK IGNITER FOR THE MAIN BURNER, A VALVE CONTROLLING THE FLOW OF GAS TO SAID BURNER, AN ELECTROMAGNETICALLY OPERATED SWITCHING MECHANISM AND AN ELECTROMAGNETIC OPERATOR WHICH OPERATES SAID VALVE AND SAID SWITCHING MECHANISM, A FLAME RESPONSIVE SWITCH MECHANISM HAVING A FIRST SWITCH CLOSED ONLY IN THE ABSENCE OF FLAME AT SAID BURNER AND A SECOND SWITCH CLOSED ONLY ON THE PRESENCE OF FLAME AT SAID BURNER, A SAFETY SWITCH HAVING A THERMAL OPERATOR ADAPTED TO MOVE SAID SAFETY SWITCH FROM CLOSED TO OPEN POSITION A PREDETERMINED TIME AFTER ENERGIZATION OF THE THERMAL OPERATOR, A CIRCUIT NETWORK COMPRISING SAID SAFETY SWITCH AND SAID FIRST SWITCH CONNECTED IN SERIES WITH EACH OTHER AND WITH TWO PARALLEL CIRCUIT BRANCHES, ONE OF SAID BRANCHES CONNECTING IN SERIES THE THERMAL OPERATOR FOR SAID SAFETY SWITCH AND THE OPERATOR FOR SAID VALVE, THE OTHER BRANCH INCLUDING SAID SPARK IGNITER, CONTROL SWITCH MEANS CONNECTING SAID CIRCUIT NETWORK ACROSS A SOURCE OF POWER, SAID SECOND SWITCH SERVING TO DEENERGIZE SAID THERMAL OPERATOR WHEN A FLAME APPEARS 0 AT THE BURNER BEFORE SAID PREDETERMINED TIME HAS ELAPSED, SAID NETWORK BEING ADAPTED UPON CLOSURE OF SAID CONTROL SWITCH TO INITIALLY ENERGIZE SAID VALVE OPERATOR, THE SPARK IGNITER, AND SAID SAFETY SWITCH OPERATOR AND, UPON THE APPEARANCE OF FLAME AT SAID BURNER, TO DEENERGIZED SAID IGNITER AND TO RETAIN SAID VALVE OPERTOR ENERGIZED, AND CIRCUIT MEANS INCLUDING SAID FIRST SWITCH FOR PREVENTING SAID MAIN VALVE FROM RE-OPENING UPON MOMENTARY DE-ENERGIZATION OF SAID VALVE OPERATOR WHILE SAID FLAME RESPONSIVE SWITCHING MECHANISM REMAINS IN HOT CONDITION, SAID CIRCUIT MEANS INCLUDING A NORMALLY CLOSED SWITCH OF SAID ELECTROMAGNETICALLY OPERATED SWITCHING MECHANISM WHICH CONTROLS ENERGIZATION OF SAID VALVE OPERATOR AND A NORMALLY OPEN SWITCH OF SAID ELECTROMAGNETICALLY OPERATED SWITCH MECHANISM SHUNTING SAID FIRST SWITCH AND SAID LAST NAMED NORMALLY CLOSED SWITCH. 